This invention relates in general to a method of selecting a trim set for a control system algorithm, and in particular, selecting a performance trim set for a vehicle control system which corresponds to a particular vehicle from a plurality of trim sets.
Many new vehicles include systems for controlling the braking of the individual wheels. Such systems can include an anti-lock braking capability to prevent wheel lock up during sudden stops and/or a traction control capability to prevent driven wheels from slipping upon low mu road surfaces. Recently, control systems have been further developed to enhance the stability of a moving vehicle.
Referring now to the drawings, there is illustrated in FIG. 1 typical brake control system 10. The system 10 is intended to be exemplary and it will be appreciated that there are other brake control systems having more or less components. In FIG. 1, hydraulic brake lines are shown as solid lines while electrical connections are shown as dashed lines. While single dashed lines are shown, it will be understood that the lines can represent a plurality of individual wires or a data buss. Additionally, mechanical connections are shown by dotted lines.
The system 10 shown is for a front wheel drive vehicle having a pair of front wheels 11 driven through a transaxle 12 by a transversely mounted engine 13. The transaxle 12 and engine 13 both include a microprocessor, 14 and 15, respectively for controlling the unit. Both front wheels 11 have associated front wheel brakes 16 which are connected though a pair of normally open solenoid actuated front isolation valves 18 to the front reservoir of a dual reservoir master cylinder 20. A pair of solenoid operated front dump valves 22 are connected to the hydraulic lines between the front wheel brakes 16 and the isolation valves 18. The front dump valves 22 are operable to bleed hydraulic fluid from the front wheel brakes 16 to an front wheel brake accumulator 24 and to an input port of a front wheel brake pump 26. The discharge of the front pump 26 is connected through a pair of check valves 28 and dump valves 22 to the front wheel brakes 16.
The rear reservoir of the master cylinder 20 is connected through a single rear isolation valve 30 and a single rear dump valve 32 to the wheel brakes 34 associated with the vehicle rear wheels 35. The rear dump valve 32 is operable to bleed hydraulic fluid from the rear wheel brakes 34 to an rear wheel brake accumulator 36 and to an input port of a rear wheel brake pump 38. The discharge of the rear pump 38 is connected through a check valve 40 and the rear dump valve 32 to the rear wheel brakes 34. Both the front and rear pumps 26 and 38 are driven by a common electric motor 42.
Usually the solenoid valves 18, 22, 32 and 36 are mounted within a control valve body (not shown). The pumps 26 and 38 also are included within the control valve body while the pump motor 42 is mounted upon the exterior of the control valve body.
The brake control system 10 further includes an Electronic Control Unit (ECU) 44 which has a microprocessor 45. The ECU 44 receives electric power through a vehicle ignition switch 46. The ECU 44 is electrically coupled to the pump motor 42, the solenoid valve coils associated with the solenoid valves 18, 22, 30 and 32 and a plurality of wheel speed sensors 47 for monitoring the speed and deceleration of the controlled wheels. The ECU 44 may also be connected to acceleration sensors 48 mounted upon directly upon the vehicle. The ECU 44 is typically mounted upon the control valve body to form a compact unit which is often referred to as an electro-hydraulic control unit.
For an Anti-Lock Bake System (ABS), the microprocessor 45 in the ECU 44 continuously receives speed signals from the wheel speed sensors 47 and any acceleration sensors 48. The microprocessor 45 monitors the wheel speed signals for a potential wheel lock-up condition. When the vehicle brakes are applied and the microprocessor 45 senses an impending wheel lock-up condition, the microprocessor 45 is operative to actuate the pump motor 42 and selectively operate the solenoid valves 18, 22, 30 and 32 to cyclically relieve and reapply hydraulic pressure to the controlled wheel brakes 16 and 34. The hydraulic pressure applied to the controlled wheel brakes 16 and 34 is adjusted by the operation of the solenoid valves 18, 22, 30 and 32 to limit wheel slippage to a safe level while continuing to produce adequate brake torque to decelerate the vehicle as desired by the driver. For traction control, the brakes are applied to the driven wheels 11 to assure that the wheel does not begin spinning on a low mu surface. Some traction control systems also communicate with the engine control microprocessor 14 to reduce engine speed and/or torque upon sensing wheel slippage. Finally, for stability control, the wheel brakes 16 and 34 are selectively actuated to maintain the vehicle upon a desired course.
A control algorithm is stored in a Read Only Memory (ROM) 49 for the microprocessor 45 in the ECU 44. The control algorithm includes the formulas and threshold values utilized by the microprocessor 45 when the control system is actuated. While a single control algorithm can be used for a variety of vehicles, the threshold values and constants loaded into the algorithm need to be selected to correspond to characteristics of the particular vehicle. Such vehicle characteristics include the vehicle weight, braking capacity, engine size, transaxle characteristics, ect. The threshold values and constants which are loaded into the control algorithm are commonly referred to as a performance trim set for the algorithm.
Typically, a specific performance trim set for a vehicle requires programming in a programmable memory, such as an Erasable Programmable Read Only Memory (EPROM), during production of the control module or when the control module is delivered to the customer. As indicated above, the trim set may provide target information for a vehicle control system, such as, a Traction Control System (TCS), a Vehicle Stability Control (VSC), and an Anti-Lock Braking System (ABS), and the like. After programming the electronic control module, the trim set would be used for the lifetime of the ECU 44 and would be valid as long as the vehicle configuration remains constant.
This invention relates to selecting a performance trim set for a vehicle control system which corresponds to a particular vehicle from a plurality of trim sets.
As described above, a performance trim set corresponding to a particular vehicle is loaded into an electronic control module. Once loaded, the trim set is fixed. Should the control module be installed in a different vehicle or a vehicle component, such as the engine and/or transaxle or transmission be changed, the algorithm would no longer be trimmed for optimal operation of the brake control system. Accordingly, it would be desirable to provide a method for matching the performance trim set to the particular vehicle components associated with the vehicle in which the control module is installed.
The present invention contemplates a method of selecting a trim set for a vehicle control system algorithm from a plurality of trim sets which includes determining a parameter related to at least one vehicle component. A trim set corresponding to the parameter is then selected and loaded into the vehicle control system algorithm.
The method also includes comparing the determined parameter to a set of allowable parameters and loading the corresponding trim set only upon the parameter being included in the set of allowable parameters. If the parameter is not included in the set of allowable parameters, an error flag is set and the control system is disabled.
The method includes sending an interrogatory message over a vehicle communication bus to the vehicle component and receiving a reply from the vehicle component which identifies the system parameter over the vehicle communication bus. In the preferred embodiment, the interrogatory message is sent to an engine control computer and the parameter is an engine identification code. Alternately, the interrogatory message is sent to a transaxle control computer and the parameter is a transaxle identification code.
The invention also contemplates determining a plurality of parameters related to a plurality of vehicle components and then selecting a trim set which corresponds to the plurality of parameters. As described above, each of the parameters so determined is compared to a set allowable parameters and the method proceeds only upon each of the parameters being included in the set of allowable parameters.
The method further includes selecting a trim set identification code, the trim set identification code being a function of the plurality of system parameters. The trim set identification code is compared to a set of allowable trim set identification codes and an error flag is set if the trim set identification code is not included in the set of allowable trim set identification codes. The trim set identification code is then utilized to select the trim set which is loaded into the control algorithm. A default trim set identification code can be selected upon closure of the vehicle ignition switch and the trim set corresponding to the default trim set identification code is loaded into the vehicle control algorithm.
It is contemplated that the algorithm can be for an anti-lock brake system, a traction control system or a vehicle stability control system.
The invention also contemplates a system for controlling at least one vehicle wheel brake which includes at least solenoid valve adapted to be connected to a vehicle brake system. A microprocessor is electrically connected to the solenoid valve and adapted to be connected to a vehicle ignition switch. The microprocessor is operative to selectively actuate said solenoid valve. The system also includes a memory associated with the microprocessor. A control algorithm for controlling the microprocessor and a plurality of sets of trim values for the algorithm are stored in the memory. The microprocessor is operative, upon closure of the ignition switch to determine a parameter related to at least one vehicle component, select a trim set corresponding to the parameter, and load the trim set into the control algorithm.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.